diff --git a/packer/environment.go b/packer/environment.go
index 4d7855dcd..2e15562e1 100644
--- a/packer/environment.go
+++ b/packer/environment.go
@@ -10,8 +10,10 @@ import (
 	"strings"
 )
 
+// The function type used to lookup Builder implementations.
 type BuilderFunc func(name string) (Builder, error)
 
+// The function type used to lookup Command implementations.
 type CommandFunc func(name string) (Command, error)
 
 // The environment interface provides access to the configuration and